To help with exploration of the ~ 5 km long, NNE trending Kimban Campoona Syncline region located on central Eyre Peninsula, to look for a large range of potentially economic basement-hosted polymetallic and other mineral occurrences including...
To help with exploration of the ~ 5 km long, NNE trending Kimban Campoona Syncline region located on central Eyre Peninsula, to look for a large range of potentially economic basement-hosted polymetallic and other mineral occurrences including iron ore, Menninnie Dam style Pb-Zn-Ag (Cu-Au) mineralisation, Ni-Co, graphite, manganese and unconformity type uranium, the Cockabidnie joint venture Project partners sought and were successful in obtaining a grant of subsidy funds under Year 1 of the SA Government's PACE 2020 Targeting initiative, to conduct strategic airborne geophysical surveying. Previously, scout aircore/RC drilling carried out by Lincoln Minerals during October 2007 and April 2008 had unexpectedly discovered sub-economic lateritic-saprolitic nickel mineralisation at sites scattered within the Campoona Syncline, which is centred about 25 km north-west of Cleve. Mineralisation grading up to 1.15% Ni + 0.33% Co + 51 ppm Sc occurs at a depth of about 15-20m beneath shallow cover, and overlies gabbroic amphibolite with up to 0.2% Ni in fresh bedrock. This mineralisation is enriched in cobalt relative to typical lateritic nickel deposits. Aeromagnetic and surface calcrete geochemical anomalies associated with it extend over a strike length of 3 km. In addition, both within and immediately west of the Campoona Syncline but still on the joint venture ground holdings, drilling done in 2007 identified significant base metal, gold and silver mineralisation grading up to 2.4% Zn+Pb, 0.26 g/t Au and 26 g/t Ag. However, because of the widely spaced drill traverses and flight line spacing of existing aeromagnetic surveys that could be applied for targeting, the inferred extent of the mineralised pods remained open both along strike and in some cases across strike. The TEMPEST time domain airborne EM method, mounted on a fixed-wing aircraft, was selected by JV operator Lincoln Minerals for acquiring the subject geophysical survey, because it is able to quickly acquire broad transects of transient EM data that are applicable to bedrock resistivity mapping plus direct detection of conductive bodies such as amphibolite intrusions and graphite-rich horizons. During July 2012, contractor Fugro Airborne Surveys flew 445 line km of TEMPEST coverage over parts of the three Cockabidnie Project licences, along east-west lines spaced 400 m apart, while maintaining a nominal 120 m mean terrain clearance. The processed AEM data was delivered by Fugro to Lincoln Minerals during October 2012. From a preliminary interpretation of the AEM data undertaken by Lincoln Minerals, several interesting EM anomalies were discerned with the X and Z channel merged data respectively, which have been depicted on interpretative geology maps included in the PACE Targeting project PT1-16 final report. In the north-western portion of EL 4883, a large EM anomaly has been deduced as representing a large saline groundwater body associated with a field of sand dunes. There is also another high amplitude EM anomaly evident in the south-west of this licence, that appears to lie along the buried contact of the Blue Range Beds with the Hutchison Group, which may possibly also be caused by accumulated saline water. Several smaller EM anomalies of particular interest were recognised in the north-western quadrant of EL 4883, lying along the Sugarloaf Hill trend where historic and recent drilling by Archer Exploration has identified graphitic schist, and where previous exploration also discovered Cu-Au anomalism in calcrete. Other EM anomalies of note are present within the Campoona Syncline, where Lincoln Minerals has intersected Ni-Co mineralisation associated with amphibolite bodies, and where some drillholes have encountered graphitic schist. Further data processing, plus anomaly identification and modelling by geophysical consultants, is planned for the AEM imagery in the coming weeks prior to commencing possible follow-up drilling.
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